In This week has been another terrible one for those of us who want a society in which all races, religions and cultures mix to their mutual advantage and enrichment.

On Tuesday, five men were sentenced to life in prison for plotting to use a huge fertiliser bomb in what would have been the UK's largest mass murder.

Omar Khyam, Waheed Mahmood, Salahuddin Amin, Anthony Garcia and Jawad Akbar - first and second generation immigrants - responded to the tolerance of the British people by trying to kill as many of them as possible.

Is it absurd to hope that the exposure of their evil after a 13-month trial which cost an estimated £50 million has finally provided the wake-up call that this slumbering country so badly needs?

Or will we continue to allow the politically-correct lunatics to stay in charge of what is becoming an asylum?

I'm one of those old-fashioned immigrants to this country who feels passionately grateful, is proudly British (as well as Irish - having been born in Dublin), and believes that immigrants have more duties than rights.

And, further, that one of those is to adjust to British society rather than expecting it to adjust to them.

However, one aspect of contemporary British society which I refuse to adjust to is its weakness in the face of the enemy within.

In my many conversations with like-minded people about the threat that radical Islam poses to the British way of lifen - and, indeed, to European civilisation - we frequently end by despairingly agreeing that the West seems intent on committing political and cultural suicide.

When we look starkly at the demographic statistics, the wimpishness of our Establishment in the face of the threat, the perversions perpetrated by political correctness and our own passivity, it's hard to avoid the conclusion that within a couple of generations, Islam will be in control in Europe.

And before anyone says that there would be nothing wrong if this happened, since the vast majority of Muslims are tolerant people who would not dream of interfering with our way of life, it's necessary to point out that in Muslim countries, it's usually the radicals and extremist mullahs - who regard tolerance as a vice - who make the running.

This occurs too in microcosm in Muslim ghettoes around Europe: we saw the frightening fundamentalist fringe of Islam marching, threatening and perpetrating violence over the publication of cartoons depicting Mohammed in Denmark while the majority of Muslims - who, yes, of course, are tolerant and decent - kept their mouths shut and stayed at home.

Yes, Islam may be a great religion. But in its fundamentalist version, some of its values are antipathetic to ours, and if they triumph in Europe, they will threaten our values such as freedom of thought and speech and the spirit of intellectual inquiry that made European civilisation great and prosperous.

The danger of ending up like those poor, despotic and medieval Islamic states in which millions live miserably is a prospect that Christians, Hindus, moderate Muslims and non-believers should be uniting to prevent. But the truth is that we are doing little to stop it.

Consider first at a few chilling statistics. Europeans are failing to reproduce. Just to keep the population steady, you need 2.1 live births per woman.

However, in 2005, the European average was 1.38. In Ireland it was 1.9, France 1.89, Germany 1.35 and Italy 1.23. Britain scored in the middle of this range with 1.6, but that was because - like France - we have a large Muslim population with a high birth rate. Indeed, Muslims are outbreeding non-Muslims throughout Europe.

"Just look at the development within Europe," said a triumphant Norwegian imam a few months ago, "where the number of Muslims is expanding like mosquitoes. Every Western woman in the EU is producing an average of 1.4 children. Every Muslim woman in the same countries is producing 3.5 children. Our way of thinking will prove more powerful than yours."

The big question this poses is: why are we not reproducing? There are many reasons, but probably the most important are the decline of religion and the liberation of women.

In Ireland, when the Roman Catholic Church effectively ran society, sex was for procreation, contraceptives were banned, the normal size for a family was around five or six children, but 12 or 13 were not uncommon.

As the country embraced secularism in the 1980s, birth rates plummeted, exacerbated by the new-found confidence of women that made them choose careers rather than domesticity.

Whereas in the 1970s, I was regarded in both the UK and Ireland as odd for being married but voluntarily childless, these days, childlessness is a common choice.

It is a world where one child families abound and to have more than two children is to be regarded as eccentric and probably environmentally irresponsible.

Moreover, the erosion of family life and the long-hours culture place a very heavy burden on those prepared to rear the next generation.

Despite these social forces, even in the UK, devout Muslims and orthodox Jews obey instructions to have large families.

Confronted with this demographic-revolution and official statistics which showed there were too few young people to support an ageing population, European governments decided to embrace immigration as an inherent good without giving any thought to the consequences.

As a result, politicians and businessmen assured us that we had to have economic growth in order to prop up ever greater public spending and that it could be provided only by importing large numbers of workers from abroad.

But why wasn't there a national debate about whether it was wise to mortgage our cultural future for the sake of a mess of financial pottage?

Where were the politicians arguing against the doctrine of multiculturalism which holds that upholding majority values is somehow illegitimate?

Who among the liberal elite's commentariat were challenging the moral relativism that flew in the face of sense and sensibility by insisting that the culture of Shakespeare, the King James Bible, Keats's poetry, Turner's paintings and Elgar's music was no more important than - and probably morally inferior to - the cultures of other imported, minorities?

We know the answer all too well. Cries of racism drowned out rational argument - not just here, but throughout old Europe.

As one gloomster put it: "Political correctness, which is to thought what sentimentality is to compassion, means that the intelligentsia of the West has disarmed itself in advance of any possible struggle."

The result of all this, as recent events have made tragically clear, was that British culture was undermined and social cohesion severely damaged.

Separated from mainstream society by geographical and cultural apartheid, which has been fostered by multiculturalism, many immigrants were denied the chance to integrate.

And, instead of being told by the host community that if they didn't want to adhere to the values of a liberal, pluralistic democracy, they should return home, they were asked how they would like Britain to conform to their values.

The story was much the same throughout Europe.

The robust American political commentator, Mark Steyn, a disillusioned Anglophile, has already written us off.

The thesis of his blackly comic book, America Alone: The End Of The World As We Know It, is that the US will survive because the religious Right are confident and reproduce, but that Europe is finished.

It's not just demographic decline, he says, it's also the unsustainability of the modern welfare state in which we depend so much on the State rather than on our own individual resources.

We are also, he believes, suffering from 'civilisational exhaustion': cultural disintegration brought about by big government which has fatally destroyed our sense of self-reliance.

Meanwhile, we are importing large numbers of unemployed youths from abroad in order to maintain our standard of living, yet many of these newcomers have nothing but contempt for our way of life and some even wish to destroy it.

Steyn sees this as a civil war which Europe is too timid even to acknowledge, let alone win. He says: "Islam has youth and will, Europe has age and welfare."

It's hard not to agree with Mark Steyn, especially as every day seems to bring more evidence that as a society we are terminally mad.

For example, this week's fertiliser bomb trial had heard that the key plotters had been radicalised by the hate preacher Omar Bakri Mohammed, whom the judge condemned as "a master of cowardice who lurked in the shadows".

This was the same firebrand who, as an asylum- seeker here, had pocketed £275,000 in welfare benefits.

Despite all this, I still believe there are grounds for hope - largely because Muslim hotheads have overplayed their hand by blowing people up, rioting in their neighbourhoods or broadcasting hate-filled speeches which alienate them from the host society.

The sharp-suited, soft-spoken undercover agents of the Muslim Brotherhood (the banned Egyptian group whose former members include Osama Bin Laden) understand that power is best secured by stealth - by infiltrating institutions and seducing the media.

Libya's Colonel Gaddafi once exemplified this policy. He said: "There are signs that Allah will grant Islam victory in Europe - without swords, without guns, without conquests. The 50 million Muslims of Europe will turn it into a Muslim continent within a few decades."

But the violent extremists have provoked some signs of a backlash, not just among the indigenous populations of Europe but among those tolerant immigrants who value the countries that took them in.

The Swedes, of all people, whom liberals claimed had produced a perfect society, are trying to row back on the welfare state, to encourage the work ethic and are demanding that immigrants integrate.

Nyamko Sabuni, a female, Muslim, African immigrant who is now the country's integration and equality minister, insists that all immigrants should learn Swedish and find a job.

She is also intent on criminalising forced marriages, checking girls for evidence of female circumcision and banning the veil, as well as state funding for religious schools. Petitions from Muslim groups demanding she be sacked have so far been resisted.

There are similar small glimmers of hope in other European countries: if Nicolas Sarkozy, the son of a Hungarian immigrant, wins the French presidential election tomorrow, he will have a mandate to restore sanity to France.

In Britain, we have bishops such as Ugandan-born John Sentamu and Pakistan-born Michael Nazir-Ali who are vigorously arguing for indigenous British and Christian values.

Above all, it is time the blunt truth was told about the dangers posed by radical Islam. We wring our hands over Iraq and blame Bush and Blair, but Al Qaeda was engaged on its murderous mission and Omar Bakri was preaching violent jihad in Britain years ago, in the days of Clinton and Major.

Right across the world, fundamentalist Muslims are fighting people of all religions as well as non-believers, because they are trying to impose their will through violence

But where is the resistance to this? In Britain, we have a consensus imposed by political correctness where such threats are not discussed. In other words, dissenting voices are censored.

The Tories are scared to talk about immigration. Worse still, they're shutting their eyes tight when it comes to confronting the Islamist threat within our midst and the need for Britain to face the threat to its cultural survival and deal with it resolutely.

Yes, the vast majority of Muslims in Britain are tolerant and law-abiding but this is no time for timidity. The enemy may be a minority but he is within, armed and dangerous and we have to deal with him.